The cost of having kids doesn't necessarily end when they turn 18 or graduate from school. In fact, a new study from Merrill Lynch and Age Wave found that 70 percent of "early adults" received financial support from their parents in the last year, and nearly 6 in 10 wouldn't be able to afford their current lifestyles without mom and dad helping to foot the bill.

Parental support for kids over the age of 25 is becoming the "new normal," but it's not just because the baby boomer generation is generous. Young adults today carry unprecedented levels of student and credit card debt, and while starting salaries aren't rising, the cost of living is. In many cases, millennials need financial help from mom and dad simply to make ends meet.

These young adults do want to get off the parents' payroll, though. According to the survey, 75 percent of early adults (ages 18-34) say becoming financially independent from their parents is the key indicator of being an adult. Women are, on average, quicker than men at accomplishing this. As this study showed, by age 30, women are half as likely as men to rely on their parents for financial assistance across nearly all expense categories, including groceries, rent, vacations, and student loans.

And for what it's worth, these grown kids are appreciative of their parents' help. Nearly 89 percent of the early adults surveyed said they'd be willing to pay it back by financially supporting their parents in the future. They might need to do that, too, because according to a new Bankrate.com report, half of parents with adult children say supporting their grown kids has jeopardized their retirement savings.

Of the parents surveyed with a household income of over $80,000, 60 percent said they've cut back on their retirement savings to help pay their adult children's bills. And of parents making less than $50,000 annually, 17 percent said they're not putting anything away for retirement (but they're still helping their grown children financially).

Parents are helping their grown children with the cost of things like health insurance, car insurance, housing, student loans, and cell phone bills. This support might come from a good place, but experts caution parents against sacrificing their own financial futures for their adult children.

"You have to decide what works best for you and then present that," said Laura Dabney, M.D., a psychiatrist specializing in interpersonal relationships in Virginia Beach, Virginia. "Start with being honest about that. And then, listen to the child—and maybe come up with a compromise. Take the two wants and needs from both sides and come up with a plan that works for everybody so there's no resentment that eventually gets in the way."

And keep in mind that prolonging financial support isn't necessarily doing your grown children any favors. As Dr. Dabney put it, "That thrill you get of stepping into adulthood—whenever you do that for your child, you're robbing them of that great joy of figuring out and doing something on their own...It can be hurtful for those children for you to be helping that much."